Optimal use of logical channels within a mobile telecommunications network

ABSTRACT

A broadcast message indicating the utilization level associated with Stand-alone Dedicated Control Channels (SDCCH) within a mobile telecommunications network serving a particular geographic area is transmitted over a broadcast channel. A plurality of mobile stations located within that particular geographic area monitoring the broadcast channel then receives the transmitted message. Thereafter, a mobile service request with a lower priority level than the indicated status level is queued by the associated mobile station and delayed until the channel utilization level rescinds to a network acceptable level.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a telecommunications network and, inparticular, to the efficient management of channel resources within adigital mobile communications network.

2. Description of Related Art

The general name of the connection between a particular mobile stationtraveling within a particular cell area and the base transceiver station(BTS) providing radio coverage for that particular cell area is the"radio interface" or "air interface". Historically, the communicationsof information across the air interface between a base transceiverstation (BTS) and a mobile station has employed, so-called, analogmodulation techniques. For example, Frequency Division Multiple Access(FDMA) technology has been widely utilized to assign each mobile stationto one of a plurality of the frequency channels associated with thecurrent cell area to communicate with the serving BTS. More recently,however, digital modulation techniques have been used in order toenhance the spectrum efficiency with which the bandwidth allotted tomobile communications is used. As an illustration, the two techniques oftime division multiple access (TDMA) and code division multiple access(CDMA) have been utilized to allow communications to proceed between aBTS and a plurality of different mobile stations on a relatively limitedamount of radio frequency bandwidth. The Global System for Mobile (GSM)communications system, for example, utilizes the TDMA concept with theallocation of one TDMA frame per carrier frequency channel tocommunicate between a mobile station and a BTS. Each frame is furthersubdivided into eight time-slots (TS). Each time-slot of a TDMA frame ona single frequency channel is referred to as a physical channel.Accordingly, there are eight physical channels per carrier in the GSMsystem. Each physical channel of the GSM system can be compared with onesingle channel in an FDMA-system, where every user is connected to thesystem via one of the associated frequencies.

The implementation of TDMA technology requires that a great quantity andvariety of information must be transmitted between the serving BTS andthe mobile station over the limited physical channels. For example,control data, service request data, actual traffic data, supplementarydata, etc., have to be communicated over the physical channels. As aresult, in order to distinguish one type of data from another, differentlogical channels have been named and mapped (assigned) on to theavailable physical channels. For example, actual speech is sent on thelogical channel named "traffic channel (TCH)" occupying one or morephysical channels. Paging of a called party mobile station is performedover the logical "paging channel (PCH)" while synchronization of amobile station with a serving BTS is performed over the logical"synchronization channel (SCH)" which occupies one of the physicalchannels. Accordingly, depending on the type of information beingtransmitted, different logical channels are utilized. Needless to say,if more physical channels are assigned to a particular logical channel,a lesser number of physical channels are available for the rest of thelogical channels.

Because of the limited physical channel resources, mobile serviceproviders are often faced with channel resource management anddimensioning problems. One such problem includes effectively managingStand-alone Dedicated Control Channels (SDCCH) within a serving mobilenetwork. Because of the fact that congestion in SDCCH logical channelsresults in lost calls and unsuccessful call setups, the efficientmanagement of SDCCH logical channels is critical for providing reliablemobile service to mobile stations traveling within the serving coveragearea.

SDCCH logical channels are not only utilized for setting up callconnections, but also for performing location updates for travelingmobile stations and for communicating packet messages containing text orgraphic data between the serving mobile network and associated mobilestations. Conventionally, all of the above mentioned functionalities areprovided the same priority and allowed equal access to available SDCCHchannel resources. As a result, all of the available SDCCH channelresources could be occupied by Short Message Service (SMS) orUnstructured Supplementary Service Data (USSD) messages transportingtext messages and could, as a result, prevent speech connections frombeing established between mobile stations and a serving mobile network.However, even though the support of all of the above mentionedfunctionalities is important for providing reliable and comprehensivemobile service to associated mobile stations, establishing callconnections is by far the most important role performed by the mobilenetwork.

Accordingly, there is a need for a mechanism to prioritize mobileservices within a serving mobile network to better utilize availableSDCCH logical channels.

SUMMARY OF THE INVENTION

The present invention discloses a method and apparatus for optimizingthe utilization of Stand-alone Dedicated Control Channels (SDCCH) withina mobile telecommunications network for high priority mobile services.The level of utilization of SDCCH logical channels is maintained withina particular base station controller (BSC) serving a particulargeographic area. After determining that such a level has exceeded athreshold value imposed by the serving telecommunications network, theBSC transmits data over a Broadcast Control Channel informing associatedmobile stations traveling within its coverage area of such adetermination. Thereafter, mobile stations wanting to request lowpriority mobile services are instructed to delay requesting one of theavailable SDCCH logical channels until the utilization level falls belowthe imposed threshold level. As a result, available SDCCH logicalchannels remain available for high priority mobile services within acongested mobile telecommunications network.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the method and apparatus of the presentinvention may be had by reference to the following detailed descriptionwhen taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a block diagram of a prior art mobile telecommunicationsnetwork illustrating a mobile station communicating with a serving basetransceiver station (BTS);

FIG. 2 is a block diagram of prior art physical channels allocated inaccordance with the Time Division Multiple Access (TDMA) technology;

FIG. 3 is a block diagram of prior art different logical channels withina TDMA physical frame in accordance with the Global System for Mobile(GSM) standard;

FIG. 4 is a signal sequence diagram illustrating the prior artcommunication of different messages for originating an outgoing callconnection;

FIG. 5 is a block diagram of a serving mobile network transmittingStand-alone Dedicated Control Channel (SDCCH) status information to amobile station in accordance with the teachings of the presentinvention; and

FIG. 6 is a flow-chart illustrating the steps performed by a mobilestation to request mobile service towards a serving mobile network inaccordance with the teachings of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a Public Land Mobile Network (PLMN) 10illustrating a mobile station 20 communicating with a serving basetransceiver station (BTS) 30. A geographic area associated with aparticular Public Land Mobile Network (PLMN) 10 is partitioned into anumber of smaller areas. Whenever a mobile station 20 travels into oneof those smaller areas known as a "location area", the mobile stationperforms a location update with the serving PLMN. Such a location updateinforms the associated mobile switching center/visitor location register(MSC/VLR) 50 of the mobile station's presence. In case the mobilestation 20 is an unregistered subscriber, a home location register (HLR)60 associated with the newly registering mobile station 20 is identifiedand necessary communication is facilitated between the serving MSC/VLR50 and the HLR 60 to authenticate the new mobile station 20. Requisitesubscriber information related to the newly registering mobile station20 is further requested and retrieved from the associated HLR 60 andstored at the serving MSC/VLR 50. Thereafter, the mobile station 20 isallowed to access mobile service within the serving MSC/VLR 50 coveragearea.

Whenever an incoming call connection is requested towards the mobilestation 20, a call setup signal, such as an Integrated Service DigitalNetwork User Part (ISUP) based Initial Address Message (IAM) is receivedby a gateway mobile switching center (GMSC) 80 associated with the HLR60. After performing HLR interrogation to ascertain the current locationof the mobile station 20, the received incoming call setup signal isrerouted by the GMSC 80 to the MSC/VLR 50 currently serving the mobilestation 20. The MSC/VLR 50 then determines the current location area ofthe mobile station 20 and instructs the appropriate base stationcontroller (BSC) 40 to page the mobile station 20. The BTS 30 then pagesthe mobile station to alert the mobile station of an incoming call. Assoon as the mobile station detects the paging message, the mobilestation 20 sends a request for a signaling channel to the BSC 40. Afterallocating an idle signaling channel to the mobile station 20, the BSC40 sends a message instructing the mobile station 20 to switch to thatparticular signaling channel. After communicating necessary control andservice related data over the newly allocated signaling channel, aspeech channel is subsequently seized and a call connection between themobile station 20 and the BSC 40 is established via the BTS 30.

Initially, the communication interface 90 between the serving BTS 30 andthe mobile station 20 employed so called analog modulation techniques.However, with the recent developments of digital communicationtechnology, digital modulation techniques are being used to enhance theefficiency and capacity of data communications within a mobiletelecommunications network. As an illustration, the techniques of timedivision multiple access (TDMA) or code division multiple access (CDMA)are being used to allow multiple communications to proceed on arelatively limited amount of radio frequencies. Global System for Mobile(GSM) based telecommunications networks, for example, utilize the TMDAtechnology with one TDMA frame per carrier frequency to communicatebetween a mobile station and a BTS.

Reference is now made to FIG. 2 depicting a diagrammatic representationof time-frame structures within the GSM standard. The longest recurrenttime period of the structure is called a hyperframe 100 and has theduration of 3 hours 28 minutes 53 seconds 760 ms. One hyperframe 100 isdivided into 2048 superframes 105, each having a duration of 6.12seconds. The superframe 105 is itself sub-divided into a number ofmultiframes. Two types of multiframes exist in the GSM standard. First,there is a fifty-one (51) frame multiframe 110 with a duration of 120ms, comprising twenty-six (26) TDMA frames 130. Next, there is atwenty-six (26) frame multiframe 120 with a duration 235.4 ms,comprising fifty-one (51) TDMA frames 140. Lastly, each TDMA framewithin a multiframe has eight time slots 150. Each of these eightphysical time slots is equivalent to one Frequency Division MultipleAccess (TMDA) channel serving a single mobile station.

A great quantity and variety of information must be transferred betweenthe BTS and the mobile station. For example, paging to inform the mobilestation of an incoming call has to be performed over one of the timeslots. A request for mobile service further needs to be communicatedover one of the time slots. Furthermore, the actual voice data must becommunicated over the available time slots. Therefore, in order todistinguish one type of information over another, different logicalchannels have been introduced and assigned to each of the eight physicaltime slots.

Reference is now made to FIG. 3 illustrating different logical channelswithin the GSM standard which can be separated into two broadcategories: traffic channels (TCH) 160 and signaling channels 170.Traffic channels (TCH) 169 are utilized by the serving BSC tocommunicate call data (e.g., voice data) with a particular mobilestation traveling within its coverage area. On the other hand, signalingchannels 170 are utilized by the serving BSC and BTS to communicateother control data necessary to implement the communication of call datawith the mobile station.

Signaling channels are further subdivided into three categories:broadcast control channels 270, common control channels 280, anddedicated control channels 280. Each of the above three categories arethen still further sub-divided into a number of logical channels fortransporting different types of information between the serving BTS andthe mobile station.

Broadcast control channels 270 are mainly utilized for communicatinginformation from the serving BTS to a particular mobile stationtraveling within its coverage area (down-link) and include the FrequencyCorrection Channel (FCCH) 180, Synchronization Channel (SCH) 190, andBroadcast Control Channel (BCCH) 200. The Frequency Correction Channel(FCCH) 180 carries information for frequency correction of the mobilestation. The Synchronization Channel (SCH) 190 carries information forframe synchronization of the mobile station and identification of theBTS. Lastly, the Broadcast Control Channel (BCCH) 200 is used tobroadcast general system information about the cell to all mobilestations located within its location area. For example, the broadcastsystem information includes data about the network that the mobilestation needs to be able to communicate with the network in anappropriate manner. Such information includes cell description, locationarea identity, neighbor cell description, etc.

Common control channels 280 include the Paging Channel (PCH) 210, RandomAccess Channel (RACH) 220, and Access Grant Channel (AGCH) 230. ThePaging Channel (PCH) 210 is used on the downlink to page a mobilestation. For example, when an incoming call setup request is received bythe serving MSC/VLR, the appropriate BSC currently serving the mobilestation is instructed to page the specified mobile station over a PCH.The Random Access Channel (RACH) 220, on the other hand, is used by themobile station to request allocation of a Stand-alone Dedicated ControlChannel (SDCCH) 240 to the BSC. For example, upon detecting the pagingmessage informing the mobile station of an incoming call, the calledparty mobile station requests a SDCCH from the serving BSC over a RACH.After allocating an idle SDCCH, the BSC utilizes an Access Grant Channel(AGCH) 230 to communicate the identity of the allocated SDCCH to therequesting mobile station.

Dedicated control channels 290 include the Stand-alone Dedicated ControlChannel (SDCCH) 240, Slow Associated Control Channel (SACCH) 250, andthe Fast Associated Control Channel (FACCH) 260. The Stand-aloneDedicated Control Channel (SDCCH) 240 is used for signaling with adedicated mobile station. Accordingly, the SDCCH 240 is the channel usedfor performing location update procedures whenever a mobile stationenters a new location area. The SDCCH is also utilized to initiate acall setup and to seize a TCH. Furthermore, SDCCH logical channels areutilized by the serving mobile network to communicate Unstructured data,such as Short Message Service (SMS) or Unstructured SupplementaryService Data (USSD) messages with associated mobile stations. The SlowAssociated Control Channel (SACCH) 250 is associated with a TCH 160 oran SDCCH 240. The SACCH 250 is a continuous data channel carryingcontinuous control information, such as measurement reports, timingadvance and power order, between the serving BSC and the mobile station.Lastly, the Fast Associated Control Channel (FACCH) 260 is associatedwith a particular TCH to work in burst stealing mode to replace speechor data traffic with other necessary signaling.

As illustrated above, with nine different types of logical signalingchannels and one logical traffic channel occupying the limited physicalchannels, the eight time slots within a TDMA frame need to be managedefficiently and effectively to provide reliable mobile service to mobilestations traveling within a particular BSC coverage area. Since logicalchannel assignments to physical channels can not be changed dynamicallyas demands for each logical channel changes within a serving network,determining the appropriate number of physical time slots to be assignedto each of the logical channels is crucial. Especially since congestionin the two of the most frequently utilized logical channels (SDCCH andTCH) results in failed call connection and lost calls. Therefore, evenafter allocating an appropriate number of physical channels to eachlogical channel, efficient management of channel resources is furthernecessary to maximize the potential utilization of available logicalchannels.

FIG. 4 is a signal sequence diagram illustrating a normal call setupprocedure in accordance with the GSM standard. Whenever a mobile station20 requests mobile service towards the serving mobile switching center(MSC) 50, either for originating an outgoing call connection or forreceiving an incoming call connection, the mobile station 20 transmits achannel request message over a Random Access Channel (RACH) towards theconnected BSC 40. After communicating with the associated MSC 50, anavailable SDCCH channel is allocated. The serving BSC 40 then transmitsan Immediate Assignment Command message 310 to the serving BTS 30 (notshown in FIG. 4) to assign the allocated SDCCH to the requesting mobilestation 20. The Immediate Assignment message 310 is further transmittedto the requesting mobile station 20 to instruct the mobile station 20 toswitch to the assigned SDCCH. Utilizing the assigned SDCCH logicalchannel, the mobile station 20 requests mobile service from the servingMSC 50 by transmitting a Ciphering Mode Service Request(CM Serv. Req.)message 320. The serving BSC 40 then sets up an Signaling ConnectionControl Part (SCCP) connection with the MSC 50 by transmitting aSCCP-Connection Request (CR) message 330. The received CM-SERV. REQ.message 320 may further be "piggy-backed" to the transmitted SCCP-CRmessage 330. The serving MSC 50 is then aware of the mobile station'srequest for mobile service. As a result, the MSC 50 attempts toauthenticate the mobile station 20 by transmitting an AuthenticationRequest message 350 to the mobile station 20 transparently through theconnected BSC 40 and over the assigned SDCCH logical channel. The mobilestation 20, in response, attempts to comply with the authenticationprocess by returning an Authentication Response message 360 to theserving MSC 50. If the authentication procedure is successfullyperformed, the ciphering mode setting procedure may be initiated by theserving MSC 50. Accordingly, the serving MSC 50 sends a Ciphering ModeCommand (not shown in FIG. 4) to BSC 40. The BSC 40, in turn, transmitsa Ciphering Mode Command message 370 including a cipher key to themobile station 20 over the assigned SDCCH logical channel. The providedcipher key is then later utilized by the serving BTS and the mobilestation to cipher and decipher digital data transmitted over the radiointerface. After storing the received cipher key, the mobile station 20returns a Ciphering Mode Complete message 380 to the serving BSC 40 overthe assigned SDCCH logical channel. The received Ciphering Mode Completemessage 390 is then transmitted to the serving MSC 50. Furthermore, inorder to guarantee the mobile subscriber's confidentiality, instead ofidentifying the mobile station with its permanently assignedInternational Mobile Subscriber Identity (IMSI) number, a TemporaryMobile Subscriber Identity (TMSI) number is further assigned by theserving MSC 50. The assigned TMSI number is then included in a TMSIReallocation Command message 400 and transmitted to the mobile station20 over the assigned SDCCH logical channel. The mobile station 20 thenconfirms the receipt of the assigned TMSI number by transmitting a TMSIReallocation Complete message 410 over the assigned SDCCH logicalchannel back to the serving MSC 50. The mobile station 20 is nowprepared to originate an outgoing call connection and transmits a CallSetup message 420 towards the serving MSC 50. The transmitted Setupmessage 420, for example, includes the directory number associated withthe intended called party subscriber. The serving MSC 50 thenacknowledges the call setup signal by transmitting a Call Confirmationmessage 430 back to the requesting mobile station 20 over the assignedSDCCH logical channel. The BSC 40 then selects an idle traffic channel(TCH) and instructs the mobile station 20 to tune to the newly allocatedTCH logical channel by transmitting an Assignment Command message 440over the SDCCH logical channel. As an acknowledgment, the mobile station20 returns an Assignment Complete message 450 back to the serving MSC 50indicating that the traffic channel is up and running. The BSC thenreleases the no-longer-needed SDCCH logical channel. An Alert message460 is then transmitted from the serving BSC 40 to the mobile station 20informing the mobile station that a ringing tone has been generated bythe serving MSC 50. Thereafter, a Connect signal 470 is transmitted fromthe mobile station 20 to the serving MSC 50. The serving MSC 50 thenacknowledges the connect signal by returning a Connect Acknowledgmentmessage 480 to the requesting mobile station 20. Thereinafter, speechconnection is established over the newly allocated TCH logical channelallowing the mobile station 20 to communicate data (e.g., voice) withits called party subscriber.

It is to be understood that the call originating procedure illustratedabove is for exemplary purposes only and that call terminationprocedures for an incoming call setup are also applicable in the sensethat the SDCCH is also needed and extensively utilized before a call canbe terminated towards its called party mobile station.

As illustrated above, until a TCH logical channel is seized enabling amobile subscriber to communicate with another telecommunicationsterminal, a great variety and quantity of information needs to beexchanged between the serving mobile network and the requesting mobilestation over a SDCCH logical channel. Such information includesauthentication data, channel assignment data, service request data, TMSInumber data, and call setup information data. Accordingly, without anavailable SDCCH channel, even if a TCH logical channel is available, amobile station is not able to access mobile service. Such mobile serviceincludes not only call setup requests as explained above but a number ofother functionalities. Each time a mobile station travels into a newlocation area being served by a new BSC, the traveling mobile stationneeds to perform a location update with its associated home locationregister (HLR) over a SDCCH logical channel. Periodically, the mobilestation then has to inform the serving BSC and MSC that the mobilestation is still within the service area by performing InternationalMobile Subscriber Identity (IMSI) Attach procedures over SDCCH logicalchannels. Terminating call connections, in a manner similar to asdescribed above, also need SDCCH logical channels to alert mobilestations and to establish terminating call connections. Furthermore,unstructured data, such as Short Message Service (SMS) and UnstructuredSupplementary Service Data (USSD) messages are also communicated overSDCCH logical channels. With all of the above described mobile servicesattempting to seize and utilize a limited number of SDCCH logicalchannels within a particular mobile telecommunications network,providing efficient and effective SDCCH logical channel resourcemanagement becomes crucial for providing reliable and efficient mobileservice to associated mobile stations.

Reference is now made to FIG. 5 illustrating a serving mobile networktransmitting Stand-alone Dedicated Control Channel (SDCCH) statusinformation to a mobile station in accordance with the teachings of thepresent invention. A telecommunications node associated with aparticular geographic area, such as a cell area, maintains statisticaldata representing the utilization level of SDCCH logical channelsassociated with that particular area. Such a telecommunications node maycomprise a base station controller (BSC) 60 serving that particulargeographic area. It may further comprise a base transceiver station(BTS) serving that particular cell area. Each time a SDCCH channel isrequested and allocated by one of the associated base transceiverstation (BTS) 30 for a particular mobile station, the statistical dataassociated with that particular cell area is updated by an applicationmodule 500 associated with the BSC 60. Similarly, each time an allocatedSDCCH logical channel is released by a mobile station, the statisticaldata is updated to reflect the availability of the released channelwithin the geographic area.

In case the maintained statistical data reflecting the level of SDCCHutilization exceeds a threshold level imposed by the associated mobiletelecommunications network, indication is noted that the level of SDCCHutilization within the serving geographic area has reached anundesirable level and there are inadequate amount of available SDCCHlogical channels remaining to adequately handle potential high-levelmobile service requests from its associated mobile stations. As aresult, the application module 500 transmits a broadcast message to allmobile stations located within its coverage area over one of itsbroadcast channels. In order to reach all mobile stations currentlytraveling within the effected geographic area, the message may betransmitted over a Broadcast Control Channel (BCCH). The transmittedbroadcast message indicates the over-utilization of SDCCH logicalchannel resources within the current geographic area and instructs thereceiving mobile stations to delay requesting low-level mobile servicefrom the serving mobile network.

As another embodiment of the present invention, a plurality of thresholdlevels may be assigned to the serving mobile telecommunications network.As an illustration, a first threshold level is assigned allowing accessto all mobile services except the lowest level mobile services, such asSMS or USSD services. A second threshold level may further be assignedto restrict the next level of mobile service. For example, locationupdates and IMSI attach may further be restricted from accessing thenetwork. The highest threshold level may then be imposed to allow onlyaccess for call connections. Such a hierarchical structure of mobileservices may be identified and determined by the service operator andfreely associated with dynamically assignable threshold values. Theserving BSC 60 then transmits an appropriate broadcast message informingthe associated mobile stations with which level the current utilizationlevel is currently associated.

Upon receiving such SDCCH status information, a mobile station wantingto request mobile service first determines whether the mobile servicehas higher priority than the received SDCCH status. If the desiringmobile service has lower priority than the current SDCCH resourcestatus, an application module 510 within the mobile station 20 queuesthe received requests. An indication to the associated mobile subscriberthat the requested mobile service is being queued and delayed mayfurther be displayed. Thereafter, the mobile station 20 periodicallymonitors the BCCH logical channel to determine whether the SDCCHutilization level has been reduced enough to allow access to the mobilenetwork. Such a determination can be made by a number of ways. Adifferent broadcast message may be transmitted by the serving BSC 60notifying the mobile stations traveling within its effective area thatthe SDCCH utilization level has decreased. As an alternative, if themonitoring mobile stations no longer receives broadcast messages overthe BCCH logical channel, a presumption is then made by the applicationmodule 510 that the restriction on the SDCCH channel request is nolonger valid. The application module 510 then retrieves the previouslyqueued request and the retrieved mobile service request is thenperformed in a conventional manner.

Reference is now made to FIG. 6 illustrating the steps performed by amobile station to comply with the SDCCH resource management procedure inaccordance with the teachings of the present invention. A broadcastchannel, such as the Broadcast Control Channel (BCCH), is periodicallymonitored by the mobile station current located within the particulargeographic area at step 500. Thereafter, the mobile station receives anindication to request mobile service towards the serving mobile network.Such an indication may include an associated subscriber entering adirectory number, service codes or function keys. Moreover, such anindication may be generated and detected internally within the mobilestation. Furthermore, such mobile service may include originating anoutgoing call connection, transmitting SMS or USSD messages, orperforming location update. In response, an application moduleassociated with the mobile station determines whether a broadcastmessage associated with the SDCCH resources has been received over theBCCH logical channel. If no such status message has been received, themobile station takes the "No" decision link 570 and performs therequested mobile service in a conventional manner at step 560. On theother hand, if such status information has been received over thebroadcast channel, the mobile station compares the priority of therequested mobile service with the received SDCCH resource status at step520. If the mobile station is requesting a service higher than the SDCCHresource status currently indicated by the received broadcast message,the mobile station takes the "No" decision link 590 and requests themobile service in a conventional manner at step 560. If, however, therequesting mobile service has lower priority than the received channelresource status, the application module associated with the mobilestation delay transmitting the request by buffering or queuing thereceived request. Such a request may be queued within a SubscriberIdentity Module (SIM) card associated with the mobile station.

Thereafter, the mobile station monitors the broadcast channel todetermine whether the channel resource utilization level has decreasedenough to enable the mobile station to request the queued mobileservice. As described previously, such a determination can be madeeither by receiving a different broadcast message indicating a lowerutilization level or by not receiving any broadcast message over apredetermined period of time. As an illustration, if the same broadcastmessage restricting the mobile station from requesting low level mobileservice is being transmitted over the BCCH logical channel, the mobilestation awaits until the restricting message is no longer received atstep 540.

After making a determination that the SDCCH utilization level hasdecreased, the mobile station then retrieves the previously queuedmobile service at step 550. The retrieved mobile service is thenrequested in a conventional manner at step 560.

Accordingly, by enabling mobile stations to comply with transmittedbroadcast messages, the serving mobile telecommunications network isable to better utilize valuable SDCCH logical channel resources for highpriority mobile service when the SDCCH utilization has exceed anundesirably high level.

Although a preferred embodiment of the method and apparatus of thepresent invention has been illustrated in the accompanying Drawings anddescribed in the foregoing Detailed Description, it will be understoodthat the invention is not limited to the embodiment disclosed, but iscapable of numerous rearrangements, modifications and substitutionswithout departing from the spirit of the invention as set forth anddefined by the following claims.

What is claimed is:
 1. A method for communicating data reflecting thestatus of channel resources to a plurality of mobile stations within amobile telecommunications network, said method comprising the stepsof:maintaining a plurality of first channels for facilitating datacommunication between a telecommunications node serving said pluralityof mobile stations and said plurality of mobile stations; firstdetermining that the utilization of said plurality of first channels bysome of said plurality of mobile stations has reached a threshold levelassociated with said telecommunications node; transmitting, in responseto said first determination, first data reflecting the scarcity of saidplurality of first channels to said plurality of mobile stations over asecond channel, said first data instructing said plurality of mobilestations to refrain until later authorized from sending requests formobile services to said telecommunications node over respective ones ofsaid plurality of first channels; second determining that saidutilization of said plurality of first channels has fallen below saidthreshold level; and transmitting, in response to said seconddetermination, second data reflecting the availability of said pluralityof first channels to said plurality of mobile stations over said secondchannel, said second data authorizing said plurality of mobile stationsto send said requests for mobile services to said telecommunicationsnode over respective ones of said plurality of first channels.
 2. Themethod of claim 1 wherein said telecommunications node is associatedwith a plurality of threshold levels and wherein said step of firstdetermining further comprises the step of determining with which one ofsaid plurality of threshold levels the utilization of said plurality offirst channels is associated and wherein said transmitted first datafurther indicates with which one of said plurality of threshold levelsthe utilization of said plurality of first channels is associated. 3.The method of claim 1 wherein said mobile services include a ShortMessage Service (SMS).
 4. The method of claim 1 wherein said mobileservices include an Unstructured Supplementary Service Data (USSD)service.
 5. The method of claim 1 wherein said plurality of firstchannels comprise Stand-alone Dedicated Control Channels (SDCCHs). 6.The method of claim 1 wherein said second channel comprises a BroadcastControl Channel.
 7. A system for communicating data indicating thestatus of channel resources to a plurality of mobile stations within amobile telecommunications network, said channel resources associatedwith a plurality of first logical channels for facilitating datacommunication between said plurality of mobile stations and atelecommunications node serving said plurality of mobile stations,comprising:an application module for maintaining said plurality of firstlogical channels; a processor for making a determination concerning theutilization of said plurality of first logical channels by some of saidplurality of mobile stations in comparison to a threshold levelassociated with said telecommunications node; and a transmitter fortransmitting, in response to said determination being in excess of saidthreshold level, first data reflecting the scarcity of said plurality offirst logical channels to said plurality of mobile stations over asecond logical channel, said first data instructing said plurality ofmobile stations to refrain until later authorized from sending requestsfor mobile services to said telecommunications node over respective onesof said plurality of first logical channels, and for transmitting, inresponse to said determination being less than said threshold, seconddata reflecting the availability of said plurality of first logicalchannels to said plurality of mobile stations over said second logicalchannel, said second data authorizing said plurality of mobile stationsto send said requests for mobile services to said telecommunicationsnode over respective ones of said plurality of first logical channels.8. The system of claim 7 wherein said mobile services include a ShortMessage Service (SMS).
 9. The system of claim 7, wherein said mobileservices include an Unstructured Supplementary Service Data (USSD). 10.The system of claim 9 wherein said first logical channels comprise aStand-alone Dedicated Control Channel (SDCCH).
 11. The system of claim 7wherein said first data are transmitted over a Broadcast ControlChannel.
 12. The system of claim 7 wherein said first logical channelsare associated with a plurality of threshold levels and wherein saidprocessor further determines, with respect to said first data, withwhich one of said plurality of threshold levels the utilization of saidplurality of first logical channels is associated and wherein saidtransmitted first data further indicates with which one of saidplurality of thresholds levels the utilization of said plurality offirst logical channels is associated.
 13. A method for communicatingdata reflecting the status of channel resources to a plurality of mobilestations within a mobile telecommunications network, said methodcomprising the steps of:maintaining a plurality of first channels forfacilitating data communication between a telecommunications nodeserving said plurality of mobile stations and said plurality of mobilestations; determining that the utilization of said plurality of firstchannels by some of said plurality of mobile stations has reached athreshold level associated with said telecommunications node; andtransmitting periodically, in response to said determination, statusinformation reflecting the scarcity of said plurality of first channelsto said plurality of mobile stations over a second channel, said statusinformation instructing said plurality of mobile stations to refrainfrom sending requests for mobile services to said telecommunicationsnode for so long as said status information continues to be transmitted.14. The method of claim 13 further comprising the steps of:determiningthat the utilization of said plurality of first channels has fallenbelow said threshold level; and discontinuing transmission of saidstatus information over said second channel to said plurality of mobilestations, said discontinued transmission of said status informationreflecting the availability of said plurality of first channels, saiddiscontinued transmission of said status information authorizing saidplurality of mobile stations to send said requests for mobile servicesto said telecommunications node over respective ones of said pluralityof first channels.
 15. The method of claim 13 wherein saidtelecommunications node is associated with a plurality of thresholdlevels and wherein said step of determining further comprises the stepof determining with which one of said plurality of threshold levels theutilization of said plurality of first channels is associated andwherein said transmitted status information further indicates with whichone of said plurality of threshold levels the utilization of saidplurality of first channels is associated.
 16. The method of claim 13wherein said plurality of first channels comprise Stand-alone DedicatedControl Channels.
 17. The method of claim 13 wherein said second channelcomprises a Broadcast Control Channel.
 18. A system for communicatingdata indicating the status of channel resources to a plurality of mobilestations within a mobile telecommunications network, said channelresources being associated with a plurality of first logical channelsfor facilitating data communication between said plurality of mobilestations and a telecommunications node serving said plurality of mobilestations, said system comprising:an application module for maintainingsaid plurality of first logical channels; a processor for making adetermination concerning the utilization of said plurality of firstlogical channels by some of said plurality of mobile stations incomparison to a threshold level associated with said telecommunicationsnode; and a transmitter for transmitting periodically, in response tosaid determination being in excess of said threshold, status informationreflecting the scarcity of said plurality of first logical channels tosaid plurality of mobile stations over a second logical channel, saidstatus information instructing said plurality of mobile stations torefrain from sending requests for mobile services to saidtelecommunications node over respective ones of said plurality of firstlogical channels for so long as said status information continues to betransmitted.
 19. The system of claim 18 wherein said transmitterdiscontinues transmission of said status information to said pluralityof mobile stations over said second logical channel in response to saiddetermination being less than said threshold level, said discontinuedtransmission of said status information authorizing said plurality ofmobile stations to send said requests for mobile services to saidtelecommunications node over respective ones of said plurality of firstlogical channels.
 20. The system of claim 18 wherein said first logicalchannels are associated with a plurality of threshold levels and whereinsaid processor further determines with which one of said plurality ofthreshold levels the utilization of said plurality of first logicalchannels is associated and wherein said transmitted status informationfurther indicates with which one of said plurality of threshold levelsthe utilization of said plurality of first logical channels isassociated.
 21. The system of claim 18 wherein said plurality of firstlogical channels comprise Stand-alone Dedicated Control Channels. 22.The system of claim 18 wherein said second logical channel comprises aBroadcast Control Channel.
 23. A method for communicating datareflecting the status of channel resources to a plurality of mobilestations within a mobile telecommunications network, said methodcomprising the steps of:maintaining a plurality of first channels forfacilitating data communication between a telecommunications nodeserving said plurality of mobile stations and said plurality of mobilestations; first determining a first priority reflecting the utilizationof said plurality of first channels by some of said plurality of mobilestations in excess of a threshold level associated with saidtelecommunications node; transmitting, in response to said firstdetermination, said first priority to said plurality of mobile stationsover a second channel, said transmitted first priority instructing saidplurality of mobile stations to refrain until later authorized fromsending requests for mobile services to said telecommunications nodeover respective ones of said plurality of first channels when saidrequests for mobile services have an associated priority less than saidtransmitted first priority; second determining a second priorityreflecting the utilization of said plurality of first channels by someof said plurality of mobile stations below said threshold level; andtransmitting, in response to said second determination, said secondpriority to said plurality of mobile stations over said second channel,said transmitted second priority authorizing said plurality of mobilestations to send said requests for mobile services to saidtelecommunications node over respective ones of said plurality of firstchannels when said associated priority of said requests for mobileservices exceeds said transmitted second priority.
 24. A system forcommunicating data indicating the status of channel resources to aplurality of mobile stations within a mobile telecommunications network,said channel resources associated with a plurality of first logicalchannels for facilitating data communication between said plurality ofmobile stations and a telecommunications node serving said plurality ofmobile stations, comprising:an application module for maintaining saidplurality of first logical channels; a processor for determining apriority reflecting the utilization of said plurality of first logicalchannels by some of said plurality of mobile stations in comparison to athreshold level associated with said telecommunications node; and atransmitter for transmitting said determined priority to said pluralityof mobile stations over a second logical channel, if the utilization ofsaid plurality of first logical channels exceeds said threshold level,said transmitted determined priority instructing said plurality ofmobile stations to refrain until later authorized from sending requestsfor mobile services to said telecommunications node over respective onesof said plurality of logical channels when said requests for mobileservices have an associated priority less than said transmitteddetermined priority, if the utilization of said plurality of logicalchannels is less than said threshold level, said transmitted determinedpriority authorizing said plurality of mobile stations to send saidrequests for mobile services to said telecommunications node overrespective ones of said plurality of first logical channels when saidassociated priority of said requests for mobile services exceeds saidtransmitted determined priority.
 25. A method for communicating datareflecting the status of channel resources to a plurality of mobilestations within a mobile telecommunications network, said methodcomprising the steps of:maintaining a plurality of first channels forfacilitating data communication between a telecommunications nodeserving said plurality of mobile stations and said plurality of mobilestations; determining a priority reflecting the utilization of saidplurality of first channels by some of said plurality of mobile stationsin excess of a threshold level associated with said telecommunicationsnode; and transmitting periodically, in response to said determination,said determined priority to said plurality of mobile stations over asecond channel, said transmitted determined priority instructing saidplurality of mobile stations to refrain from sending requests for mobileservices to said telecommunications node for so long as said statusinformation continues to be transmitted when said requests for mobileservices have an associated priority less than said transmitteddetermined priority.
 26. A system for communicating data indicating thestatus of channel resources to a plurality of mobile stations within amobile telecommunications network, said channel resources beingassociated with a plurality of first logical channels for facilitatingdata communication between said plurality of mobile stations and atelecommunications node serving said plurality of mobile stations, saidsystem comprising:an application module for maintaining said pluralityof first logical channels; a processor for determining a priorityreflecting the utilization of said plurality of first logical channelsby some of said plurality of mobile stations in comparison to athreshold level associated with said telecommunications node; and atransmitter for transmitting periodically, in response to saiddetermined priority reflecting the utilization of said plurality offirst logical channels in excess of said threshold, said determinedpriority to said plurality of mobile stations over a second logicalchannel, said transmitted determined priority instructing said pluralityof mobile stations to refrain from sending requests for mobile servicesto said telecommunications node over respective ones of said pluralityof first logical channels for so long as said determined prioritycontinues to be transmitted when said requests for mobile services havean associated priority less than said transmitted determined priority.